An inertia cone crusher may be utilized for efficient crushing of material, such as stone, ore etc., into smaller sizes. An example of an inertia cone crusher can be found in EP 2116307. In such an inertia cone crusher material is crushed between an outer crushing shell, which is mounted in a frame, and an inner crushing shell, which is mounted on a crushing head. The crushing head is mounted on a crushing head shaft. An unbalance weight is arranged on a cylindrical sleeve-shaped unbalance bushing encircling the crushing head shaft. The cylindrical sleeve is, via a drive shaft, connected to a pulley. A motor is operative for rotating the pulley, and, hence, the cylindrical sleeve. Such rotation causes the unbalance weight to rotate and to swing to the side, causing the crushing shaft, the crushing head, and the inner crushing shell to gyrate and to crush material that is fed to a crushing chamber formed between the inner and outer crushing shells.
In order for an inertia cone crusher to be able to function correctly, the crusher should operate under load, i.e. the crushing chamber should be continually fed with material to be crushed. Material is fed into the crushing chamber via a feeding hopper and the level of the material in the feeding hopper is controlled to minimize the risk that the feeding hopper is emptied while the crusher is still operating. If an inertia cone crusher operates without material, or with too little material, inside the crushing chamber the crushing shells may be damaged by the crushing head. Thus, when an inertia cone crusher is stopped, the crushing chamber is usually full of material, to avoid that the crushing shells are demolished by the crushing head.